1. Field of the Invention
This invention concerns a coin discrimination method and device, and in particular concerns a coin discrimination method and device to perform discrimination of genuine and counterfeit coins and of coin types, based on the pattern of the surface and other parts of the coin.
2. Description of the Related Art
Coin discrimination devices used in automatic vending machines and similar generally employ a sensor using a magnetic coil to detect the material, outer diameter, surface pattern and other parameters of a coin to discriminate among coins. The detection signals output from this sensor are concentrated in a basic pattern representing the characteristics of the coin; by comparing this basic pattern with basic patterns established in advance, the genuine or counterfeit nature of the coin, and the coin type, are discriminated.
However, recently there have appeared altered coins which are foreign coins, similar in material and shape, and machined such that the magnetic pattern matches that obtained from genuine coins; as the machining precision of these altered coins increases, it has become more difficult to discriminate between genuine and counterfeit coins by means of a magnetic sensor.
Consequently there is increasing demand for coin discrimination devices which use optical sensors or similar to capture a two-dimensional image of the coin surface, and perform pattern matching of the captured two-dimensional image with known coin patterns to perform coin discrimination.
However, when an image sensor captures the image of the surface of a coin which moves by rolling at high speed along a coin pathway, the image of the surface of the coin is blurred, and there have been such problems as an inability to obtain a clear two-dimensional image sufficient for coin discrimination, and difficulties in clearly capturing, over the entire face of the coin, a pattern formed only from slight protrusions and depressions on the coin surface.
Further, the captured two-dimensional image of the coin surface is a rotated image due to the rotation of the coin; when performing pattern matching, the rotation angle of the acquired two-dimensional image must be detected and corrected, and so there is the problem that processing time is lengthened.
As technology to resolve such problems, the xe2x80x9ccoin discrimination devicexe2x80x9d described in Japanese Patent Application Laid-open No. 8-180235, and the xe2x80x9ccurrency discrimination devicexe2x80x9d described in Japanese Patent Application Laid-open No. 6-274736, and similar have been proposed.
An object of the present invention is to provide a coin discrimination method and device which enable the stable and reliable capture of the image of a coin surface, and which are capable of competent discrimination processing of the coin using a two-dimensional image of the coin surface.
In order to achieve the above object, the invention comprises a coin discrimination method for discriminating coins which roll along a coin pathway, wherein, when the coin reaches a prescribed position of the coin pathway, a surface or an edge of the coin is illuminated with light, a still image of the illuminated surface or edge is captured, and based on the captured still image, discrimination of the coin is performed.
The invention also comprises a coin pathway as a light-blocking space.
The invention also comprises a still image which is captured by a two-dimensional image sensor.
The invention also comprises a two-dimensional image sensor as a MOS-type image sensor.
The invention also comprises an image capture means which begins the image capture operation in advance, before the coin reaches the prescribed position.
The invention also comprises image information which corresponds to a pattern on a top side or on a bottom side of a coin to be discriminated, which rolls along a coin pathway, is captured, and the coin to be discriminated is discriminated based on the captured image information; wherein the image information for the top side or the bottom side of the coin to be discriminated is separated into areas set in advance, a specific pattern is extracted from one of the separated areas, and based on the extracted specific pattern, a judgment is made as to whether the coin to be discriminated is a prescribed coin or not.
The invention also comprises image information which is a binary image, in which a pattern based on the pattern of the top side or the bottom side of the coin to be discriminated is drawn in white or in black, and the separation is performed by drawing separation lines of a prescribed width, in a color opposite the pattern color, in preset positions of an image representing the image information.
The invention also comprises separation lines, being circles having the same center as the coin to be discriminated.
The invention also comprises image information which corresponds to an image which has been corrected for rotation such that the coin to be discriminated faces a prescribed reference direction, and the separation lines are straight lines.
The invention further comprises a coin discrimination method in which image information corresponding to a pattern of a top side or a bottom side of a coin to be discriminated, rolling along a coin pathway, is captured, and the coin to be discriminated is discriminated based on the captured image information; wherein at least two specific patterns are extracted from the image information of the top side or the bottom side of the coin to be discriminated, and using a relative positional relation between the extracted specific patterns as a characteristic quantity, discrimination of the coin to be discriminated is performed.
The invention further comprises a characteristic quantity which includes a distance between centers of gravity of the respective extracted specific patterns.
The invention also comprises a characteristic quantity which includes angles formed by line segments connecting a center of the coin to be discriminated, and centers of gravity of each of the specific patterns.
The invention also comprises specific patterns that are extracted from binary images obtained by conversion of the image information to binary level.
The invention also comprises image information which is separated into a plurality of patterns, and the specific patterns are extracted based on areas of each of the separated patterns.
The invention also comprises image information that is separated into a plurality of patterns, and the specific patterns are extracted based on distances between centers of gravity of each separated pattern and a center of the coin to be discriminated in the image information.
The invention also comprises a distance between centers of gravity of the specific patterns that is normalized based on a radius of the coin to be discriminated in the image information, and discrimination of the coin to be discriminated is performed using this normalized distance as the characteristic quantity.
The invention may comprise a coin discrimination device for discriminating a coin rolling along a coin pathway, comprising illumination means, placed at a prescribed position on the coin pathway, for illuminating with light for a short time a surface or an edge of the coin rolling along the coin pathway; image-capture means for capturing an image of the surface or edge of the coin, illuminated with light from the illumination means; image-capture start indication means, for indicating a start of image capture to the image-capture means in advance, before the coin reaches a image-capture position of the image-capture means; and, light emission indication means, for indicating a start of illumination of light to the illumination means when the coin reaches the image-capture position of the image-capture means.
The invention also may comprise an image-capture start indication means that comprises a first sensor, positioned on an upstream side of the illumination means on the coin pathway, and the light emission indication means comprises a second sensor, positioned corresponding to the image-capture means.
The invention also may include a coin pathway which constitutes a light-blocking space.
The invention also may include an image-capture means which is a two-dimensional image sensor.
The invention also may include a two-dimensional image sensor that is a MOS-type image sensor.
The invention also may comprise a coin discrimination device which acquires image information corresponding to a pattern of a top side or a bottom side of a coin to be discriminated which rolls along a coin pathway, and discriminates the coin to be discriminated based on the acquired image information, comprising: separation means for separating the image information for the top side or the bottom side of the coin to be discriminated into areas set in advance; specific pattern extraction means for extracting specific patterns from among any of areas separated by the separation means; and judgment means for comparing specific patterns extracted by the specific pattern extraction means with reference values, and for judging whether or not the coin to be discriminated is a prescribed coin.
The invention also may comprise image information as a binary image, in which a pattern based on the pattern of the top side or the bottom side of the coin for discrimination is drawn in white or in black, and the separation means separates the pattern by drawing separation lines of a prescribed width, in the color opposite the pattern color, in preset positions in the binary image.
The invention also may include structure wherein the separation means draws, in the image, circles having the same center as the coin for discrimination as the separation lines.
The invention also may comprise a structure wherein the image information corresponds to an image subjected to rotation correction such that the coin to be discriminated faces a prescribed reference direction, and the separation means draws on the image straight lines as separation lines.
The invention also may comprise a coin discrimination device, in which image information corresponding to a pattern on a top side or a bottom side of a coin to be discriminated, rolling along a coin pathway, is acquired, and the coin to be discriminated is discriminated based on the acquired image information, comprising: specific pattern extraction means for extracting specific patterns from image information for the top side or the bottom side of the coin for discrimination; pattern-to-pattern distance computation means for computing a distance between at least two specific patterns extracted by the specific pattern extraction means; and judgment means for judging the coin for discrimination based on the distance calculated by the pattern-to-pattern distance computation means.
The invention also may comprise a pattern-to-pattern distance computation means which computes the distance between centers of gravity of the respective specific patterns extracted by the specific pattern extraction means.
The invention also may comprise angle computation means for computing angles formed by a plurality of line segments joining each of centers of gravity of at least two specific patterns extracted by the specific pattern extraction means with a center of the coin to be discriminated in the image information, and wherein the judgment means judges the coin to be discriminated based on the angles computed by the angle computation means.
The invention also may include a specific pattern extraction means which comprises image conversion means for converting to binary level the image information for the top side or the bottom side of the coin to be discriminated, and the image conversion means extracts the specific patterns from the binary-level image.
The invention also may include a specific pattern extraction means which comprises pattern separation means for separating the image information into a plurality of patterns, and area computation means for computing an area of each pattern separated by the pattern separation means; and patterns, areas of which as computed by the area computation means are within a range set in advance, are extracted as the specific patterns.
The invention also may include a specific pattern extraction means which comprises pattern separation means for separating the image information into a plurality of patterns, and position specification means for specifying positions of patterns separated by the pattern separation means based on a distance between center of gravity of the patterns and a center of the coin to be discriminated in the image information; and patterns, positions of which as specified by the position specification means are within a range set in advance, are extracted as the specific patterns.
The invention may also include normalization means for normalizing the distance between the specific patterns based on a radius of the coin to be discriminated in the image information, and wherein the judgment means judges the coin to be discriminated based on comparison of the distance normalized by the normalization means with a reference value.
By means of this invention, the coin pathway is configured such that light is blocked and there is illumination by light for a short time when the coin reaches the image-capture position, and in addition, the image sensor is caused to begin image capture in advance before the coin reaches the image-capture position. Hence the image of the surface of the coin rolling at high speed can be captured in a manner close to the stationary state, and an image free of omissions can be captured.
Separation lines set in advance are drawn on a binary image acquired from the top side or from the bottom side of the coin, arranged so as to separate the pattern; hence linking of patterns by various factors can be prevented, without changing the conditions for binary-level conversion.
Further, the device is configured such that a plurality of prescribed patterns are detected from the image of the top side or of the bottom side of the coin, and the coin is discriminated based on the distance between the centers of gravity of each of the detected patterns, so that discrimination of the coin can be performed without correcting for the rotation angle of the image of the rolling coin.